In a storage system, e.g., in a personal storage product or enterprise storage product, a hard disk is the most frequently replaced field replaceable unit. A typical problem encountered by storage vendors is that: some of the hard disks that are returned from the field may have been tested with a good performance. The reason being that storage vendors make such decisions of failing a hard disk in accordance with single-sourced health data provided by the hard disk, for example, only in accordance with the collected S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology) report or I/O (input/output) operation error statistics of the hard disk. However, the single-sourced health data may not be sufficient to reflect overall health condition of the hard disk, and the decision made according to the single-sourced health data causes a hard disk that may be operating perfectly, to be replaced. Such erroneous judgment will cause increase of an erroneous judgment rate on the hard disk's health condition and thereby cause frequent replacement of hard disks and increase of costs, and also cause other parts in the storage system that may have actually failed not to be replaced in time. Another problem resulting from deciding whether the hard disk should be replaced according to the single-sourced health data is a missing judgment of hard disk errors.